This invention relates to display systems and, more particularly, to devices which alter the display at selected locations by controlling a cursor over the display.
Engelbart, in U.S. Pat. No. 3,541,541 describes an X-Y position indicator control for movement by the hand over any surface to move a cursor over the display on a cathode ray tube. The indicator control mechanism of the Engelbart device contains X and Y position wheels mounted perpendicular to each other, which rotate according to the X and Y movements of the mechanism, and which operate rheostats to send signals along a wire to a computer which controls a CRT display.
The Engelbart device is a promising one for altering a display pattern on a cathode ray tube. The use of the cursor allows the operator to accurately indicate the exact position on the display on which he can make alterations. The X-Y position indicating device is a practicable mechanism for controlling the position of the cursor relative to the display pattern.
A disadvantage of the Engelbart device is that its movement over a surface is dependent upon the movement of the X-Y position wheels themselves. Hence, the device is biased to move in X and Y directions respective to the planes of the X and Y position wheels.
Rider, in U.S. Pat. No. 3,835,464, provides an X-Y position indicator for controlling a cursor over a visual display which is not biased in any given direction of movement. The position indicator includes a transport sphere in combination with position wheels for supporting the indicator and translating its movement into Cartesian coordinates.